Science & Tech

Understanding High-Energy Cosmic Rays with Amaterasu Particles

  • In May 2021, Japanese scientists made a big scientific discovery when they identified an ultra-high-energy cosmic ray dubbed ‘Amaterasu’ after the Japanese sun goddess.

Discovery of Amaterasu

  • Dr. Toshihiro Fujii, an astronomer from Osaka Metropolitan University, found the Amaterasu cosmic ray.
  • Amaterasu has an exceptionally high energy level of 240 exa-electron-volt (EeV).
  • When compared to man-made accelerators, this energy is approximately 40 million times greater than that of protons accelerated by the Large Hadron Collider (LHC).

The Mysterious Origin of Amaterasu

  • Amaterasu seemed to have sprung from an empty region of the universe.
  • Theories advanced by Dr Fujii include an undiscovered source, interaction with a strong magnetic field, and the need for new physics models.
  • Previous Records: The “Oh My God” particle, discovered in 1991 with an energy of 320 EeV, is still the most energetic cosmic ray ever discovered.

The Nature and Impact of Cosmic Rays 

  • Cosmic rays are streams of energetic particles, including protons and alpha particles, that originate in space and from the sun.
  • Interaction with Earth: The majority of cosmic rays lose energy in the Earth’s atmosphere, preventing hazardous high-intensity rays from reaching the surface.
  • Historical Importance: Since the 1930s, studies of cosmic rays have led to the discovery of numerous subatomic particles, albeit their sources and high energy remain unknown.

Cosmic Ray Types and Origins

  • GCR (Galactic Cosmic Rays): Coming from outside our solar system, maybe from supernovae.
  • Cosmic Rays of the Sun: Emitted by the sun, particularly in solar flares, and predominantly composed of protons.
  • Composition Analysis: Studies demonstrate that the helium-to-hydrogen nuclei mass ratio in cosmic rays is similar to the composition of the early cosmos.

The Effects of High-Energy Cosmic Rays

  • UHECRs (ultra-high-energy cosmic rays): Extragalactic particles having energy greater than 1 EeV.
  • Space Travel Limitations: UHECRs with more than 60 EeV energy experience suppression owing to contact with cosmic microwave background (CMB) radiation, limiting their travel distance to 50-100 megaparsecs.
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